RF ion guide with axial fields

摘要

RF ion guides are configured as an array of elongate electrodes arranged symmetrically about a central axis, to which RF voltages are applied. The RF electrodes include at least a portion of their length that is semi-transparent to electric fields. Auxiliary electrodes are then provided proximal to the RF electrodes distal to the ion guide axis, such that application of DC voltages to the auxiliary electrodes causes an auxiliary electric field to form between the auxiliary electrodes and the ion guide RF electrodes. A portion of this auxiliary electric field penetrates through the semi-transparent portions of the RF electrodes, such that the potentials within the ion guide are modified. The auxiliary electrode structures and voltages can be configured so that a potential gradient develops along the ion guide axis due to this field penetration, which provides an axial motive force for collision damped ions.

主权项

1. An apparatus, comprising:
an ion source; a mass analyzer; and an RF ion guide positioned in an ion path between the ion source and the mass analyzer, the RF ion guide having an ion guide axis extending between an input end of the RF ion guide and an exit end of the RF ion guide, the RF ion guide comprising: a first electrode extending along the ion guide axis, the first electrode configured to be connected to a voltage source; and a second electrode extending along the ion guide axis, the second electrode configured to be connected to a RF source, a portion of the second electrode being positioned between the first electrode and the ion guide axis, the second electrode comprising a plurality of openings, wherein during use of the apparatus, the second electrode produces RF electric fields within a central portion of the RF ion guide throughout a region between the second electrode and the ion guide axis to radially confine ions, wherein the first and second electrodes are configured so that during operation of the RF ion guide, a DC electric field is generated between the first and second electrodes, resulting in a DC electric field at the ion guide axis that has a non-zero axial component.